Question: Which of these numbers is prime? ${22,\ 45,\ 83,\ 85,\ 93}$
Explanation: A prime number has exactly two factors: 1 and itself. The factors of 22 are 1, 2, 11, and 22. The factors of 45 are 1, 3, 5, 9, 15, and 45. The factors of 83 are 1 and 83. The factors of 85 are 1, 5, 17, and 85. The factors of 93 are 1, 3, 31, and 93. Thus, 83 is a prime number.